A series of MnO_2-supported noble metal catalysts (Pd/MnO_2、Ru/MnO_2、Ag/MnO_2 and Pt/MnO_2) with a noble metal loading of 3.0% were synthesized by redox precipitation. The catalytic oxidation ability of CO followed the order: 3.0%Pd/MnO_2>3.0%Ru/MnO_2>MnO_2>3.0%Ag/MnO_2>3.0%Pt/MnO_2. To understand the relationship between activity and textures of the catalysts, characterization techniques such as HRTEM/HAADF-STEM, XRD, Raman, H_2-TPR, O_2-TPD and XPS were employed to analyze the particle size of noble metals, crystal structure, defection structure, low-temperature reducibility, active oxygen species and elemental composition of the catalysts. The tests indicated that the support of Ag or Pt simply promoted the low-temperature reducibility of MnO_2. However, Ag and Pt on the catalyst surface were rapidly reduced by CO, leading to partial deactivation. In contrast, supporting Pd or Ru not only enhanced low-temperature reducibility but also created abundant surface chemisorption oxygen species. The superior CO catalytic oxidation ability of 3.0%Pd/MnO_2 and 3.0%Ru/MnO_2 was attributed to the combined effect of low-temperature reducibility and abundant surface chemisorption oxygen species. The 3.0%Pd/MnO_2 catalyst exhibited a lower reduction temperature and a greater abundance of surface chemisorption oxygen species, enabling complete oxidation of a 1%CO/4%O_2 reaction gas mixture at 10 ℃ (GHSV= 40000 mL/(g·h)). It was speculated that the CO catalytic oxidation mechanism of 3.0%Pd/MnO_2 followed the Langmuir-Hinshelwood (L-H) model.